System-on-a-chip or System on Chip (SoC or SOC) is an idea of integrating all components of a computer or other electronic system into a single integrated circuit (chip). It may contain digital, analog, mixed-signal, and often radio-frequency functions—all on one chip. A typical application is in the area of embedded systems.
Secure environment for processors have been already disclosed, in particular with respect to multi-processing architecture. For example, a solution to limit the access to a secure memory was described in the document WO04015553. According to this solution, the processor has two modes of operations; in the first mode, called the secure mode, access is permitted to the secure memory; and in the unsecure mode, the access to the secure memory is forbidden. The unsecure mode is intended to development purposes, i.e. testing or debugging the circuit. During the execution in unsecure mode, the access to the secure memory is physically blocked, i.e. a “disable” signal is generated. This “disable” signal forbids any attempt to access the secure memory.
Another solution is described in the document PCT/EP2000/056145 in which a single chip descrambling processor processes the scrambled audio/video data in order to never leave access to the clear data. When the descrambling operation is done, the descrambling unit comprises an encryption engine to encrypt the descrambled data before they are temporarily stored in an external memory. When the processor finishes the organization task, the data are decrypted in the output module and sent to the displaying device